Data Link Connector (DLC)
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Cadillac Escalade EXT. However, it is still accessible from the selected car via links, so may be relevant.
The data link connector (DLC) provides serial data communication for ECM diagnosis. This connector allows the technician to use a scan tool in order to monitor various serial data parameters, and display DTC information. The DLC is located inside the driver's compartment, underneath the instrument panel.